The present invention relates to a process for the preparation of phosphate surfactants. More particularly, the invention relates to an improved process for the preparation of surfactants containing a hydroxypropylene phosphate group.
The phosphate substituted surfactants include phosphobetaines of the formula ##STR1## wherein A is selected from O.sup.-, OM and --O--Y--R.sup.+
B is selected from O.sup.- and OM PA0 X.sup.- is an anion PA0 Z is an integer from 0 to 2 with the proviso that only one of A and B can be O.sup.- and Z is of a value necessary for charge balance, PA0 R is an amine or an amidoamine reactant moiety, and PA0 Y is alkylene or substituted alkylene. PA0 X is an anion PA0 Z is an integer from 0 to 3, a value necessary for charge balance, PA0 R is an amine or amidoamine moiety, and PA0 Y is alkylene or substituted alkylene. PA0 (1) reacting an inorganic phosphate salt with epichlorohydrin to obtain a phosphate ester alkylating agent; and PA0 (2) reacting said phosphate ester alkylating agent with a substituted amine to obtain the desired phosphate substituted compound PA0 B is selected from O.sup.-, OM and H PA0 X is an anion PA0 n is an integer of 1 or 2 PA0 Z is an integer from 0 to 3 as required for charge balance. PA0 R.sub.2 is hydrogen or alkyl, hydroxyalkyl or alkenyl of up to 6 carbon atoms each or cycloalkyl of up to 6 carbon atoms, or polyoxyalkalene of up to 10 carbon atoms, PA0 R.sub.3 and R.sub.4, which may be the same or different, are selected from alkyl, hydroxyalkyl, carboxyalkyl of up to 6 carbon atoms in each alkyl moiety, and polyoxyalkylene of up to 10 carbon atoms; in addition, R.sub.3 and R.sub.4 taken together with the nitrogen to which they are attached, may represent an N-heterocycle, e.g., a moropholino structure, in which the Y radical is bonded to a ring atom of said N-heterocycle other than the nitrogen of the R moiety; PA0 n is an integer from 2 to 12; PA0 Y may be alkylene, optionally interrupted by up to 3 oxygen atoms, of up to 12 carbon atoms, which alkylene chain may optionally be substituted with lower alkyl, alkoxy, hydroxy or hydroxyalkyl, e.g., of not more than 10 carbon atoms each; PA0 M is hydrogen, an organic radical selected from alkyl or hydroxyalkyl of up to 6 carbon atoms, polyhydroxyalkyl of up to 10 carbon atoms, glceryl, cycloalkyl of up to 6 carbon atoms, aryl or arylalkyl of up to 10 carbon atoms, or a salt radical selected from alkali metals (e.g., sodium, potassium, or ammonium and substituted ammonium radicals) and alkaline earth metals (e.g., magnesium or calcium).
These phosphobetaine surfactants are fully described in U.S. Pat. No. 4,215,064 which is incorporated herein by reference.
The phosphate substituted surfactants also include phosphitaines of the formula ##STR2## wherein R is an amine or an amidoamine reactant moiety and Y is alkylene or substituted alkylene. These phosphitaine compounds are more fully described in U.S. Pat. No. 4,261,911 which is incorporated herein by reference.
The phosphate substituted surfactants may also include pyrophosphobetaines of the formula ##STR3## wherein A is selected from O.sup.-, OM and O--Y--R.sup.+ with the proviso that at least one A is O.sup.-
These pyrophosphobetaine compounds are more fully described in U.S. Pat. No. 4,382,036, which is incorporated herein by reference.
The phosphate substituted surfactants described above all exhibit outstanding foaming, viscosity-building, wetting, cleansing, detergency, anti-static and emulsifying properties and are, therefore, useful in industrial applications calling for high performance surface active agents. The compounds are also highly stable species and are extremely well tolerated by human tissue, i.e., they exhibit exceptionally low ocular irritation and oral toxicity, and are, therefore, eminently suited and useful as surface active agents in personal care compositions, such as shampoos, conditioners and the like.
In the preparation of the various phosphate substituted compounds set forth above, the processes generally comprise two steps: (1) reaction of an inorganic phosphate salt with epihalohydrin to yield a phosphate ester alkylating agent and (2) reaction of a substituted amine with the phosphate ester alkylating agent to form the desired phosphate substituted compound.
In U.S. Pat. No. 4,283,542 which describes processes for the preparation of phosphobetaines, there is a general description of the above process. In column 11 of that patent, a process is described comprising the reaction of epichlorohydrin with phosphoric acid and various phosphate salts. The most important reaction parameter is said to be the pH of the phosphate salt. It is said that the pH must be strictly controlled and "The desired pH range is from 4 to 5. If the pH drops below 4, there is significant hydrolysis of the phosphate ester. If the pH at which the reaction is run is too high, there will be a loss of labile organic chlorine. When the reaction is carried out in an alkaline environment of a pH 9.5-10.5 optionally, the resulting intermediate had surprisingly lost its labile organic chlorine and formed a cyclic diester . . . The phosphate salt used should have the pH of 9.5-10.5 before the addition of epichlorohydrin. This will allow for maximum formation of the cyclic phosphate diester." The yields are relatively low for this described process.